Scum skimmer



Feb. 11, 1958 A. WORMSER ETAL 2,822,928

SCUM 'SKIMMER 2 Sheets-Sheet 1 Filed Dec. 24. 1954 Feb. 11, 1958 A. WORMSER ETAL 2,822,928

SCUMSKIMMER Filed Dec. 24. 1954 2 Sheets-Sheet 2 0\\\\\\\ 'Vllll' (IIIIIII/II/A United States Patent SCUM SKIMMER Arthur Wormser, Lawrence A. McKinney, Irvin W. Ma-

hacek, and Jack E. Haston, Tucson, Ariz., assignors to Infilco Incorporated, Tucson, Ariz., a corporation of Delaware Application December 24, 1954, Serial No. 477,492 8 Claims. (Cl. 210-523) This invention relates to a device for removing floatable matter'from liquids, such as the skimming of froth from the surface of liquid clarifiers.

An object of the invention is to provide an improved skimming device for use in treating tanks, such as settling basins, flotation units, or other liquid treatment apparatus.

Another object of this invention is to provide an improved skimming device wherein the skimmer blade conforms to the face of the ramp of a scum trough sufficiently to prevent the floating material from forming a wedge on the ramp and the blade from sliding over the material.

Another object of the invention is to provide a skimming device wherein a maximum amount of floating material with a minimum amount of liquid is carried up the ramp of a scum trough by the skimmer blade.

Other objects will be apparent from the description and the claims which follow.

The skimming device of the present invention is adapted for use in liquid treating apparatus of all types in which it is desired to remove floating material. The skimmer will.

be described for purposes of illustration, but not of limitation, as used in connection with a circular clarifier in which flotation is employed to promote the clarification of the liquid being treated. However, it will be'understood that the basin need not be round, but may have a different configuration.

In the treatment of liquid, and particularly in the treatment of waste liquids by flotation, the impurities in the liquid rise to the surface of the liquid in the form of a scum or froth, being commonly termed float. This float must be removed from the surface of the liquid and discharged to waste, or further treated to recover any valuable constituents.

Various methods have been used for removing the froth or float from the surface of the liquid. For example, skimmers used therefor usually comprise a vertical rotatable shaft in the center of the tank, a skimmer arm attached thereto, and a scum scraper or bladefixed to the skimmer arm. As the skimmer arm rotates about the tank center, the blade pushes scum toward a scum trough, which usually extends radially inwardly from the outer wall of the tank. The upper edge of the scum trough is ordinarily placed above the surface of the liquid so that the liquid cannot drain into the trough. Upon the forward edge of the trough, that is, the direction from which the skimmer arm approaches, is placed a ramp sloping from the upper edge of the trough down below the surface of the liquid. When the blade reaches the ramp, it will push the scum up along the ramp and into the scum trough, from which it can be removed by any suitable means. In order to make the blade conform to the face of the ramp, the blade frequently has been made of flexible material, with the result that the blade had a tendency of sliding over float on the ramp rather than pushing it into the scum trough.

The present invention provides a scum skimmer which ethciently removes the scum from the liquid without removing a large volume of the liquid itself.v Briefly, the

invention comprises a skimmer blade that is mounted on a rotatable skimmer arm in a manner such that it is free to move, within predetermined limits, with respect to the skimmer arm and therefore to the surface of the ramp, so that the lower edge of the blade progressively and freely adjusts itself to the surface of the ramp as it rises thereon until it is in contact therewith for its full length. T he blade, therefore, may be made of rather stiif material so that it pushes the float up the ramp to the trough, and does not ride over it.

The invention will be more readily understood by ref- I scale, on line 44 of Figure 1.

The squeegee 51 extends below the skimmer blade. and.

- As shown in Figure 1, a clarifier 10 has a circular upstanding wall 11 to which is rigidly fixed, as by welding,

a scum trough 12 in such manner that the wall 11 forms one end wall of the trough 12. One side wall of the I trough 12 is formed by a vertical plate 13 that projects radially inwardly from the wall 11. The other end wall of the trough 12 ,is formed by a plate 14, made, in the shape of an arc of a circle, which has an extension piece 15 that serves as a baflle plate. the trough 12 is formed, as best seen in Figure 2, by the plate sections 16 and 17 and the ramp 18. The upper edge 20 of the ramp 18 also extends radially of the clarifier 10. The lower or leading edge 21 of the ramp 18 is parallel to the upper edge 20. The bottom 22 of the trough 12 slopes downwardly from the end wall 14 to the wall 11 of clarifier 10 in order that float that collects in the trough moves readily out of it through the outlet 23 in the wall 11.

A drive shaft 25 is located in the center of the clarifier 10 and is driven by any suitable means, such as a motorreducer, not shown. Rigidly connected to the drive shaft 25 is a bracket 26 to which is fixed a skimmer arm 27. As best seen in Figure 3, a bar 28 is pivotally connected to skimmer arm 27. The pivot connection generally indicated at 30 includes a hub 31 which is fixed to the bar 28 and into which is pressed a bushing 32. A hollow spacer 33 is inserted into the bushing so that it projects out of the bushing 32 at both ends. Thrust Washers 34' are placed on the projections of spacer 33. A pivot pin or bolt 35 has a retaining washer 36 placed on it, and the bolt 35 is passed through the spacer 33 and a hole in the skimmer arm 27. A nut 37 and a lock washer 38 complete the pivot connection.

Fixed to the bar 28 on opposite ends thereof are brackets 41 to which are pivotally connected links 42 by any suitable means, such as pins 43. Each link 42 is provided with an extension 44 which projects beneath the skimmer arm 27 so that the end 45 of the extension provides a stop that limits the lower position of the links 42. Extension 44 is adjustably fixed against link 42 by means of a pivot connection 46 and a bolt 47 that is fixed to extension 44 and passes through a slotted hole 48 in link 42. After the proper adjustment of the extension 44 is made with respect to the link 42, a nut is tightened on bolt 47.

Rigidly connected to the links 42 is a skimmer blade 50 in such manner that the blade 50 extends on a radius of the clarifier 10. While the skimmer blade itself can be used for skimming, we prefer to provide a squeegee 51, fixed to the skimmer blade 50 by means of a keeper 52.

Patented Feb. 11,- 1958 The other side wall of also projects laterally'of the skimmer blade at both ends. The portion of the squeegee 51 that does not project laterally of the skimmer blade 50 is made of relatively stiff material; but the portion of the squeegee 51 that does extend laterally of the skimmer blade 50is made of relatively flexible material,- so that'it -wil'l'readilyyield when p it comes in contact with the extensionpiece of end wall 14 and the wall 11 of clarifie'r 10:

While the-side wall 13-of trough -12, the upper edge of the ramp 18, and'theblade 50 are shown for purposes of exemplificationas extending radially of the clarifier, all three membersmay be made tangentto a circle concentric with the clarifier 10.

Guides 55 are placed across the trough fromthe upper edge 20 of the-ramp 18 to the=top of the side'1'3 so-that the blade is carried across-the'trough Without dropping into it. In order to prevent splashing as the skimmer blade 50 is returned dOWIPil'llG'lhB-Hqllid', ramp members 56-arefixed to the top of'the-sidewall 13 leading-down into the liquid.

The operation of the skimmer will be readily understood. As'the skimmer arm27 and blade 50 are rotated in the clarifier 10, and before-the squeegee 51 reaches the After the squeegee 51 has come in line contact with ramp 18- and while it'continues'to rise'higher'onthe ramp, the end 45 of extension 44 of the inner link 42 loses contact with the skimmer arm 27. Simultaneously, the bar 28 rotates in a clockwise direction and the line contact between the squeegee 51 and the ramp increases until finally the squeegee is in contactwith the ramp over its entire length. As soon as thefullzlength of the squeegee is in contact with the ramp, the float in front of the blade 50 is'trapped' and'is prevented from escapingrearwardly or sidewiseas iris-pushed up the ramp. Asthe squeegee approachesthe upper edge 20 ofthe ramp 18, it gradually becomes more nearly parallel to the ed'ge20,

- thereby approaching a. level. plane; .At, the. instantzthe squeegee 51 is about to pass over the upper edge 20 of the ramp 18, it isinconta'crwith,audparallel to, the edge 20 over its entire length. The squeegee 51 then crosses the scum trough 12, resting on the guide members. 55,

1' moves over'the side wall13', and .isloweredback into the loweredge 21 of the ramp 18,- the blade 50 is hanging down in the 'lowermosst position permitted by the ends 45. Preferably the extensions 44 are adjusted so that their ends-=45 are in contactwit-h the underside. of-the skimmer arm when the-lower edge of the squeegee S1- is in the same horizontal plane asthelower edge 21 of the ramp 18. As the blade-50 is rotated, the outer edge of the squeegee 51- is in contact with the wall 11, and the float .on the surface of the liquid is pushed. forward in the direction of the arrowin Figure 1 toward the ramp18' of the scum trough 12. As :the blade approachesthe ramp 1%, it-also contacts the extension piece 15 of the end wall 14, thereby enclosing the float in front of the blade between the wall 11, the extension piece 15, the blade 50 and the ramp 18. The first contact'between the squeegee 51 and the lower edge 21 of the ramp 18 occurs at the innermost point of the edge 21. The squeegee 51 moves progressively onto the ramp 18, and simultaneously the weight on the bar 28 .is relieved between the inner end of the bar and the pivot connection 30. The end of the extension-440f the inner link 42 remains in contact with the underside of the skimmer arm 27 as the bar 28 rotates about. the pivot 30 in counterclockwise direction, looking'in the direction of the arrow in Figure 1, while the end 45 of the extension 44 of the outer link 42 moves down away from the skimmer arm 27. As a result of this action andJbeCause"the pivot connection 30 is spaced closer to theinner link 42 than to the outer link 42, the squeegee 51 drops at its outer end while the-inner end continues to-rise along the ramp 18. The inner edge of squeegee .511will .be-flexed due to the resulting sidewise movement. However, because of the extension of its outer edge the .squeegeewillremain .in contact with the wall 11 and the vrxtensionpiece 15. During this initial stage of travel of the skimmer ."uptheramp 18, the only point on the lower edge of thelsqueegee 51 that is in contact with the ramp 1.8 .is' the innermost end, while that. portion of the squeegee 51 between .the innermost end and the point just passing over edge .21 rises above the .face of the ram 18 so as to form therewith a small triangular gap. This gap becomes first progressively largerand then. smaller as the point of contact of the innermost end of the squeegee rises on the face of the ramp 1.8. When the innermost end of the squeegee .51: reaches acertain. point up on the face of the ramp 18, line contact is established and the triangular gap nolonger exists. The position of the blade on the ramp when line contact is established is a function (a) of the ratio of "the distances between the F pivot 30 and the inner and outer. :link 42, trespactively; (b) of the ratio of the distances from the blade 50 .and'

from the stops 45 toa vertical plane' through pivots 43;? and (c) of the locationof the" links 42 with :respect to the ends at theblade 50. 1

liquid down then-amp members 5.6.

This action of the skimmer mechanism involves a minimum amount of flexing of the squeegee 51, thereby allowin'g'the squeegee to bemade of rather stiff material. Such a stiff squeegee 'is capable of moving much larger amounts of float up the ramp '18 than the usual flexible squeegees. However, the lateral edges of the squeegee 51' which extend beyond the blade should be of soft, pliable material 'sotha'ttbe' lateral'movement of the blade 50' due to the relative motion between the blade 50 and the skimmer arm 27 will'not'berestricted.

Many modifications of the invention shown for exemplification'and illustration 'couldbe' made without departing from the scopeand' spirit of the-invention. Thus, while onetrough and skimmer arm and blade have been shown, it will be understood that, depending on such variables as the size ofthe-ciarifier and the quantity and consistencyv of'the float, more than one trough and more than one skimmer arm and blade may be needed. Accordingly,.we do not'wish to limit ourselves to the exact structural details shown and described herein.

We claim:

1. Ina device for-removing scum from a basin having a scum trough including a sloping ramp member on its leading side, said ramp member having a leading edge and a trailing edge parallel to one another, said device comprising a skimmer arm adapted to be rotated in said basin, a skimmer blade rotatable with said arm, said ramp member andblade extending inwardly from the periphery-of saidflbasin -for such a length that said blade approaches said leading edge at an angle and does not conform to the surface of said ramp member, the combination with said blade of connecting means between said arm and said 'bladepermitt-ing said blade to swing aboutahorizontal axis and to moveangularly withrespect to said skimmer arm when saidbladecontactsand moves up said sloping ramp member, said connecting means including a-plurality of parallel link members, each link member -being-rigidly connectedtosaid blade and being pivotallyconnected with said arm, whereby said blade canadjust itself to-the surface of said ramp member as it rises thereon.

'2. A scum skimmer for a basin provided with ascum trough having a ramp sloping upwardly to its leading edge, saidl ramp havinga leading edge and a trailing edge parallel to one another, said scum skimmer comprising a skimmer arm rotatable in said basin, and a skimmer blade rotatable with said am, said ramp and blade extending inwardly from the periphery of said basin :for such a lengththat said bladeapproaches-said leading edge at an angleanddoes not'conform to the surface of said ramp,

characterized by connecting means between said armand said blade permitting said "blade to move an-gularly to, and about the longitudinal axis .of, :said arm,.-saidcounectingf :means comprising :a :bar, a single. pivot connecting said ibarfco said arm, and .a pair of parallel links, each link beingv pivotally connected withcne end 'to said bar,

and rigidly connected with the other end to said blade, whereby said blade can adjust itself to the surface of said ramp as it rises thereon.

3. In a liquid treating apparatus comprising a tank provided with a scum trough having an open top and including a ramp member leading upwardly to said open top and having an upper edge, extending along a major portion of a radius of said tank, an improved device for moving scum from said tank into said trough, said device comprising a skimmer arm adapted to be rotated in said tank, a bar pivotally connected to one point of said skimmer arm, a pair of parallel links pivotally connected to opposite end-s of said bar, said links being provided with stop members that contact said skimmer arm to limit the downward movement of said links, a skimmer blade rigidly connected to said links and extending along a major portion of a radius of said tank, and a squeegee fixed to said blade so as to extend below the lower edge thereof.

4. The apparatus of claim 3, wherein said squeegee is of stifi material and has lateral extensions beyond said blade of flexible material.

5. The apparatus of claim 3, wherein said stop members are adjustable.

6. An improved device for moving scum accumulated in a basin into a scum trough having a sloping ramp memher, said device comprising a skimmer arm adapted to be rotated in said basin, a bar, a pivot connecting said bar to said skimmer arm, a pair of parallel links pivotally connected to said bar on opposite sides of, but unequally spaced from, said pivot, stop means limiting the lowermost position of said links, and a skimmer blade rigidly connected to the free ends of said links.

7. A device for moving floatable material from a circular basin into a scum trough fixed to the wall of said basin, said scum trough including a ramp member leading upwardly to the upper edge of said trough and bounded on its sides by the wall of the basin and an extension of an end wall of said trough, said device comprising a central rotatable drive shaft in said basin, said drive shaft being adapted for connection to a prime mover, a skimmer arm rigidly connected to said drive shaft at an elevation above said scum trough, a bar, a pivot connecting said bar to said skimmer arm, a pair of brackets aflixed to said bar adjacent each end, a pair of parallel links pivotally sup ported by said brackets, a skimmer blade rigidly connected to the free ends of said links, and stop means adjustably fixed to said links to limit the lower position of said skimmer blade so that in its lowermost position its lower edge lies in the same horizontal plane as the bottom of said ramp member, said pivot being laterally offset with respect to said brackets.

8. A device according to claim 7, wherein a stiff squeegee is afiixed to said blade.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,266 Morehead Apr. 27, 1937 2,249,049 Sayers et al. July 15, 1941 2,279,970 Coe Apr. 14, 1942 2,513,111 Schiller June 27, 1950 2,611,489 Scott Sept. 23, 1952 

